Photolithography, also known as optical lithography, is a crucial process used in manufacturing integrated circuits and microelectromechanical systems (MEMS). It involves using light to transfer a pattern onto a photoresist layer on a substrate, typically a silicon wafer. The process begins with coating the substrate with a photosensitive material called photoresist. A photomask, containing the desired pattern, is placed over the photoresist, and light is shone through it, exposing certain areas. The exposed areas undergo a chemical change, becoming either soluble or insoluble in a developer solution. After development, the pattern is transferred onto the substrate through etching, chemical vapor deposition, or other processes.
The technology has evolved from mercury arc lamps to deep ultraviolet (DUV) and extreme ultraviolet lithography (EUVL). EUVL, using a 13.5 nm wavelength, has revolutionized the semiconductor industry, enabling the fabrication of features at 7 nm and smaller. ASML is the sole supplier of EUV lithography equipment. The process can create extremely small patterns, down to a few nanometers, providing precise control of shape and size. In complex integrated circuits, a wafer may undergo the photolithographic cycle up to 50 times. Recent advancements focus on improving resolution, efficiency, and sustainability. These include high-resolution photoresists and advanced thin films.
